This invention relates to the cephalosporin class of antibiotics. In particular, this invention relates to a process for preparing 3-halomethyl-3-cephem compounds from 3-methylenecephams.
3-Halomethylcephems are known in the cephalosporin art and have proved to be useful intermediates for the preparation, via nucleophilic displacement of the halogen atom, of many related cephalosporin antibiotic compounds. 3-Halomethylcephems have heretofore been available by allylic halogenation of the corresponding desacetoxycephalosporin compounds (U.S. Pat. Nos. 3,637,678 and 3,705,897) and by halogenation of the corresponding desacetylcephalosporins (U.S. Pat. No. 3,658,799). More recently 3-halomethylcephems have been prepared by cleavage of 3-acetoxymethyl and 3-carbamoyloxymethyl cephems with hydrohalic acids [S. Karady, T. Y. Cheng, S. H. Pines and M. Sletzinger, Tetrahedron Letters, 30, 2625 (1974)].
It is an object of this invention to provide a novel process for the preparation of 3-halomethylcephems from 3-methylenecephams.